1. Field of the Invention
The present invention relates to film packages in which a sheet of photographic film is removably contained in a light-shielding envelope.
2. Background
A known photographic film package, mainly used by professional photographers, includes a relatively large film sheet, e.g., 12.5.times.10 cm film sheet, which is contained in a light-shielding envelope. For example, a film package disclosed in U.S. Pat. No. 4,821,054 comprises a film unit contained in a light-shielding envelope. The film unit consists of a carrier sheet having a light-locking clip secured to its trailing end for closing an open trailing end of the light-shielding envelope, and is formed at its leading end with a tab disposed eccentrically relative to the carrier sheet's longitudinal center line. A photographic film sheet is detachably adhesively attached to the carrier sheet at an intermediate region. The light-shielding envelope has numbers "1" and "2" printed on the leading end section thereof, such that a zone, which does not overlie the tab, is indicated by the number "1", whereas a zone which overlies the tab is indicated by the number "2". A part of the tab or a part of inner surface of the light-shielding envelope facing the tab is provided with a cold-adhesive agent.
The above described film package is inserted into a film holder, which is disposed on the back of a cooperating camera, through an access opening, such that the light-locking clip is placed into an innermost position in the film holder opposite to the access opening. In this state, the leading end section of the light-shielding envelope having the numbers "1" and "2" protrudes from the film holder. When a lock lever of the film holder is actuated, the light-locking clip is arrested in the film holder. In order to take a photographic picture, the light-shielding envelope is grasped at zone "1" and pulled out from the film holder. Because the zone "1" does not overlay the carrier sheet, the light-shielding envelope is moved relative to the film unit, so that when the light-shielding envelope has been pulled out to a predetermined position, the film sheet is uncovered. In this state, the film package is ready for photographing. After photographing, the light-shielding envelope is inserted back into the holder by grasping the zone "1" until the open end of the light-shielding envelope is closed by entry thereof into the light-locking clip, so that the film sheet is recovered by the light-shielding envelope in light-tight fashion. Thereafter, the lock lever is released so as to enable removal of the film package from the film holder. When removing the film package, zone "2" is grasped. Because zone "2" overlies the tab of the carrier sheet, the light-shielding envelope and the film unit are together grasped and are removed from the film holder by pulling the light-shielding envelope. At that time, because the light-shielding envelope is adhered at the zone "2" to the tab when grasped, relative movement between the light-shielding envelope and the carrier sheet is prevented. For development, the photographic film sheet is peeled away from the carrier sheet.
In the above described conventional film package, the gripping zone for withdrawal of the light-shielding envelope only is distinguished from that for removal of the whole film package. However, as the light-shielding envelope must be grasped at the designated zones in a predetermined sequence, handling of the conventional film package is rather cumbersome and, therefore, the photographer tends to mishandle it. According to conventional photographic film packages, the light-shielding envelope containing the exposed photographic film sheet is folded along a line extending transversely near the leading end section of the light-shielding envelope, and is sealed by an adhesive tape, so as to distinguish the exposed film package from unexposed film packages, as well as to prevent the exposed film sheet from being mistakenly re-exposed. However, is possible that the adhesive tape may become accidentally detached because of the resiliency of the light-shielding envelope.
Furthermore, it is possible that adhesive agent for detachably attaching the photographic film sheet to the carrier sheet may seep out from the end of the film sheet onto the photosensitive emulsion layer of the photographic film. In such a case, the photosensitive emulsion layer would be removed from the film base when the film sheet is peeled away from the carrier sheet. If the adhesive agent should extend to the end surface of the photographic film, a backing layer for preventing the film sheet from curling is also removed from the film base with the removal of the film sheet.
When the conventional film package is used in a dusty room or outside on a windy day, dust or particles tend to accumulate inside of the film holder. If there is dust or particles in the film holder, since the back surface of the film sheet uncovered from the light-shielding envelope will be in contact with the inner wall of the film holder, the dust or particles would adhere to the back of the film sheet, and would provide grazes on the film sheet when the film sheet is pushed into the light-shielding envelope.
As the film package is a disposable photographic film, the light-shielding envelope is made of carbon black filled paper material so as to reduce the cost of the film package. However, such a paper light-shielding envelope is not only insufficient in stiffness, but also would be curled or curved when stored in a damp room for a long time preventing smooth insertion of the film package into the film holder.
The above described light-locking clip is secured to the carrier sheet by caulking, but not to the degree that the light-locking clip will slip out of the carrier sheet when the light-shielding envelope is pulled out. Furthermore, the light-locking clip may be so deformed when caulked, that the open end edges thereof are too close to each other to arrest the light-locking clip in the film holder.